A previous reseller of the Ionovac in Germany, Otto Braun, created an updated plasma tweeter in 1978. His company Corona Acoustic developed the Corona type 314-514. Again a slight misnomer as this was a plasma tweeter and not a corona based speaker, but close. It is similar to the Ionovac in that a plasma is created in a quartz tube which is horn loaded and driven by local circuitry at the rear. Their description of its operation differs from what may be found here for plasma tweeters as it doesn't include any thermal characteristics in the explanation, it is described more closely to an ion wind speaker. That doesn't quite fit but we can agree to disagree as these devices are difficult to classify.